Two aging, fracture-critical bridges in Hastings and St. Cloud will be torn down and replaced, after the Minnesota Department of Transportation on Thursday moved the bridges to the top of its construction list.

The DeSoto Bridge on Hwy. 23 in St. Cloud, which was closed March 20 after bent gusset plates were found, will be demolished this summer, with a new bridge scheduled to open November 2009.

And MnDOT now wants to begin the process for replacing the troubled Hwy. 61 bridge in Hastings, with construction to start in 2010.

The safety of both bridges had been an issue of mounting concern after the Aug. 1 collapse of the Interstate 35W bridge in Minneapolis.

Thursday's announcement was a contrast to months of assurances from MnDOT that the state's aging bridges, the Hastings span in particular, were worthy of continued service.

Sen. Katie Sieben, DFL-Newport, said MnDOT's decisions on the two bridges stemmed from the 35W disaster in which 13 people died and moe than 100 were injured.

"Even though we're not sure yet why it collapsed, it did point out that we as a state needed to invest in our infrastructure in a serious manner,'' Sieben said.

In particular, the replacement of the Hastings bridge wouldn't have been expedited without this year's transportation spending bill, which the Legislature passed despite Gov. Tim Pawlenty's veto, Sieben said. "We now have the money to do it,'' she said.

Acting Transportation Commissioner Bob McFarlin said Thursday that the St. Cloud bridge "is a little bit unique," although he credited the infusion of state funds with moving up some projects. "Whether the bill had passed or not, we would have examined very closely our ability to advance that into this construction season given the fact that it's closed."

He stressed that speeding the replacement process for the Hastings bridge was not because of any immediate safety issue and noted that the bill mandates the state to replace certain types of bridges by 2018. He called the timing a matter of "opportunity and inevitability."

Dan Dorgan, the state's bridge engineer, said that the St. Cloud bridge's gusset plates now appear to have been bent not from unusually heavy loading, but from the time of construction 50 years ago. They could have been reinforced over seven weeks at a cost of $325,000, he said.

Because of its age and its fracture-critical design, however, the steel truss bridge had been a candidate for replacement in the next several years, so state and local officials prefer the $35 million replacement.

"The new bill made our financial analysis of that situation easier," McFarlin said.

From 2018 to 2010

The decision to begin construction of a new bridge over the Mississippi River at Hastings by 2010 is a stark departure from MnDOT's previous stance.

Hastings Mayor Paul Hicks said MnDOT informed the city in January 2007 that there would be no new bridge until at least 2018 and maybe not until after 2020.

Rather than any acute finding that the bridge is in trouble, MnDOT's reversal is a matter of money and greater scrutiny of bridge decisions in the aftermath of last summer's collapse, Hicks said.

"There is more of a jaundiced eye toward looking at bridges now,'' the mayor said.

Both Hicks and Sieben also credited the turnaround to pressure on MnDOT from a coalition of citizens, business interests, politicians, city staff and others concerned about the bridge's deterioration and traffic hazards.

"It's overdue,'' said Hastings Police Chief Mike McMenomy. "A lot of people right now are reluctant to drive over it.''

State bridge inspection reports from 1997 through 2007 indicate that the structure's physical condition has worsened over the years as MnDOT has deferred maintenance work on corrosion, broken bearings, rotting sidewalks and crumbling concrete. Like the 35W bridge and the DeSoto Bridge, the 58-year-old Hastings Bridge is fracture-critical, meaning that if one steel beam or connection breaks, the whole thing could fall down.

McMenomy said a months-long repair project scheduled for this spring and summer should temporarily alleviate fears about the structural integrity of the bridge. But a greater risk to public safety is traffic volume -- a problem that won't be solved until the new four-lane bridge is built to replace what is now the state's busiest two-lane bridge, McMenomy said.

25 steel truss bridges

There are 25 steel truss bridges on the state highway system, Dorgan said, and they've been undergoing the same three-part review that the St. Cloud bridge had: an evaluation of the bridge's load rating, a recalculation of the numbers used in the bridge's original design and, if necessary, a visual inspection.

It was a visual inspection that led to the Hwy. 23 bridge's abrupt closure last month, when workers saw bowing of about a quarter-inch in four of the bridge's gusset plates.

State officials originally thought the bending was the result of "load issues," but Dorgan said Thursday that the deformation was probably because of "original fit-up issues" -- in other words, it probably happened when the bridge was built.

The current St. Cloud bridge won't reopen. Dismantling should begin in June or July, with major construction beginning in September and completion set for November 2009.

'Heightened awareness'

With steel bridges representing about 34 percent of the nearly 600,000 highway bridges in the United States, people across the country are saying "maybe we should be more worried about this," said Henry Petroski, a professor of civil engineering and history at Duke University.

"What happened in Minnesota is drawing a lot of attention,'' Petroski said. "It has created heightened awareness and that makes people reluctant to cut corners.''

The members of Congress whose districts include the bridges applauded the state's decision to replace them. Rep. John Kline and Rep. Michele Bachmann, both Republicans, also noted that the projects won't be funded with earmarks, the much-criticized congressional practice of directing federal money to favored projects.

Kline said that hundreds of millions of federal dollars that are not earmarked already come to Minnesota, so MnDOT "should have the ability to set the priority for those federal dollars ... without the intrusion of any earmarking."